<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .box {
            width: 1200px;
            overflow: hidden;
            margin: 40px auto;
        }

        .box ul {
            list-style: none;
        }

        .box ul li {
            float: left;
            width: 380px;
            height: 210px;
            margin-right: 20px;
            /* 子绝父相 */
            position: relative;
        }

        .box ul li img {
            width: 380px;
            height: 210px;
        }

        .box ul li .info {
            position: absolute;
            width: 370px;
            height: 30px;
            line-height: 30px;
            color: white;
            bottom: 0;
            padding-left: 10px;
            background-color: rgba(0, 0, 0, .5);
            /* 透明度设置为0，不是背景的透明度，而是整体的透明度 */
            opacity: 0;
            /* 过渡 */
            transition: opacity 2s ease 0s;
        }

        /* 当li被触碰的时候，内部的info盒子就要把透明度变为1 */
        .box ul li:hover .info {
            opacity: 1;
        }
    </style>
</head>

<body>
    <div class="box">
        <ul>
            <li>
                <img src="images/0.jpg" alt="">
                <div class="info">北京的故宫</div>
            </li>
            <li>
                <img src="images/1.jpg" alt="">
                <div class="info">鸟巢国家体育场</div>
            </li>
            <li>
                <img src="images/2.jpg" alt="">
                <div class="info">十七孔桥</div>
            </li>
        </ul>
    </div>
</body>

</html>